Ophthalmology in horses encompasses the study and treatment of eye disorders and diseases affecting equine species. Equine ophthalmic conditions can range from conjunctivitis and corneal ulcers to more complex issues such as uveitis and cataracts. These conditions can impact a horse's vision and overall well-being. Diagnostic techniques in equine ophthalmology include visual examinations, fluorescein staining, and advanced imaging methods like ultrasonography. Treatment approaches vary depending on the specific condition and may involve medication, surgical intervention, or supportive care. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, pathology, diagnostics, and treatment modalities related to equine ophthalmology.
Alter GM.In an effort to assess the influence that crystallization may have on protein conformations, optical absorption spectra of crystalline state hemoglobin derivatives have been examined. These spectra were obtained from photoacoustic spectra using a computer-assisted analysis. Comparisons of crystal and solution state hemoglobins using crystal minus solution state difference spectra indicate that the conformations of these proteins are similar in both states. Crystallization does not change the absorption properties of horse oxyhemoglobin or the cyanide and azide adducts of horse and human methem...
Floyd K, Suter PF, Lutz H.Direct staining of the granules of blood eosinophils by anti-immunoglobulin fluorescein isothiocyanate (FITC) conjugates was observed when feline blood smears were tested for presence of feline leukemia virus (FeLV) antigen by immunofluorescent antibody. When blood smears of other species including swine, horses, cattle, dogs, sheep, birds, and human beings were examined, direct staining of eosinophils by FITC conjugates was also detected. This FITC staining was restricted to eosinophils and was not observed in neutrophils, lymphocytes, and platelets. Direct FITC staining of eosinophils does n...
McLaughlin SA, Brightman AH, Helper LC, Manning JP, Tomes JE.In 123 cases of external ocular disease in the horse, pathogenic microorganisms isolated with greatest frequency were Streptococcus sp (43.9%), Staphylococcus sp (24.2%), and Pseudomonas sp (13.8%). Fungi were isolated in 4.8% of the cases. In vitro testing showed that most of the Streptococcus sp isolants were sensitive to ampicillin, cephalothin, and carbenicillin. Most of the Staphylococcus sp isolants were sensitive to gentamicin, cephalothin, and bacitracin. Most of the Pseudomonas sp isolants were sensitive to polymyxin B and gentamicin.
Neumann SM, Kainer RA, Severin GA.In the main study, hyperthermia was induced by radio-frequency current to obtain a single, central, corneal lesion in the right eye and 2 separate limbal lesions in the left eye of 13 light horses and 8 ponies. Intracorneal and intralimbal temperature profiles for the procedure were obtained in a separate study from the eyes of a horse and a pony treated in the same manner. After treatment of the principal eyes and 6 sham-treated eyes, clinical observations were conducted for up to 6 months, using indirect ophthalmoscopy, biomicroscopy, and fluorescein staining. Immediately after hyperthermic ...
Rebhun WC, Mirro EJ, Georgi ME, Kern TJ.Habronemic blepharoconjunctivitis was characterized clinically by raised yellow gritty plaques in the palpebral and bulbar conjunctivae. Lid granulomas and blepharitis were observed in some cases. On histologic examination, mast cells, eosinophils, and collagenolysis was found in most sections, but if only one section was examined an erroneous diagnosis of mastocytosis could have been made. Treatment consisted of larvicidal mixtures for lid lesions and organophosphate ophthalmic drops along with corticosteroids for the conjunctivitis. If the cornea was damaged by the gritty conjunctival plaque...
Holmberg DL.Four horses with corneal perforations of various etiologies were presented for surgical correction. Pedicle grafts taken from the bulbar or palpebral conjunctiva were used to repair the defects. Two horses regained functional vision in the affected eyes while a third had significant impairment. The fourth eye, which had an intense uveitis pre and postoperative, became phthisic and blind.
Bistner SI, Riis RC.Several manifestations of equine corenal ulcers caused by mycotic agents are discussed. Antifungal therapy is reviewed. Mycotic keratitis should be suspected when routine corneal ulcer therapy is nonproductive.
Murphy J, Young S.Sudden unilateral blindness occurred in a 7-year-old grey gelding Quarterhorse. Ophthalmoscopy revealed a pigmented mass arising from the nasal ciliary body of the right eye and extending around the posterior surface of the lens, and there were pigmented particles in the vitreous. Examination of the enucleated globe showed a circumscribed, black, dense and symmetrically ovoid mass with sessile attachment to the nasal ciliary region and extension to posterior lens capsule, vitreous and along the vitreal face of the detached retina to the optic papilla. The mass was composed of heavily pigmented...
Mason TA.Two cases of bilateral atresia of the nasolacrimal orifice are described. The presenting sign was a persistent ocular discharge, clear in the one case and purulent in the other. Treatment by the creation of a fistula between the distal extremity of the blind ending duct and the nasal cavity was successful in both cases.
Anderson BG, Anderson WD.Methyl methacrylic casts were prepared and tissue was freshly collected for histologic examination to compare the vascular supply and the structure of the vessels of the iris in the adult horse with those of the dog. In the horse, ciliary blood vessels divided in the iris and formed a complete major arterial circle of the iris. In the dog, the ciliary blood vessels divided in the ciliary body and, by means of recurrent branches, formed a complete arterial circle. From this circle, radial arteries extended toward the pupillary margin. The radial vessels in the horse were nearly straight and joi...
Smith JS, Mayhew IG.The sympathetic nervous innervation of the head was surgically transected in the horse, cow, sheep and goat. The site of transection was preganglionic in all 4 species and ganglionic-postganglionic in 2 additional horses. The Horner's syndrome, manifested as a result of the iatrogenic lesion, varied with the species. Ptosis was the most constant sign in all species. Unilateral sweating over the face and proximal neck, particularly at the base of the ear, was the most prominent feature in the horse. The cow revealed distension of vasculature and cutaneous heat of the pinna, and a reduced produc...
Beard WL, Wilkie DA.Ocular and periorbital sarcoids and squamous cell carcinoma are common in equine practice. Extensive involvement of periorbital tissues often necessitates removal of the globe if the function of the eyelids can not be maintained with tumor removal alone. This report describes a modification of the standard enucleation or exenteration technique for cases in which there is insufficient skin to achieve primary closure following complete surgical excision. The caudal portion of the dorsal orbital rim is protuberant; partial excision with an osteotome facilitates skin closure by decreasing the size...
Cooley PL.When compared with small domestic animals, the horse has unique ocular characteristics (complete bony orbit, well-developed eyelid muscles, a nasal and temporal gray limbal line, granulae iridica, paurangiotic fundus). Knowledge of normal equine ocular anatomy is essential for ocular lesion interpretation. It is important to obtain a full history and general examination before sedation, nerve blocks, or other diagnostic ophthalmic tests are performed. All ocular examinations should include a systematic evaluation of both the anterior and posterior segments. Selection of other diagnostic tests ...
Finno CJ, Eaton JS, Aleman M, Hollingsworth SR.A 23-year-old female mule was presented for bilateral ocular abnormalities and an abnormal pelvic limb gait. Results: Anisocoria, unilateral enophthalmos, medial strabismus, ptosis, pupillary light reflex deficits, and bilateral reticulated pigmentary retinopathy were observed on ophthalmic examination. Neurologic abnormalities included right-sided facial nerve paralysis, extensive symmetric muscle atrophy, and asymmetric pelvic limb ataxia with an abnormal pelvic limb gait. A positive titer (1:40) for equine protozoal myeloencephalitis (EPM) associated with Neospora hughesi was obtained from ...
Angeluci GC, Ricci CL, Passareli JVGC, Estanho GJG, Oliveira AS, Santos SGA, Giuffrida R, Rodrigues M, Andrade SF.Measurement of the intraocular pressure (IOP) is a useful diagnostic tool in equine ophthalmology. Handheld tonometers, such as Tonovet and Tonovet Plus (rebound), Tono-Pen AVIA Vet (applanation), and Kowa HA-2 (applanation using the Goldmann methodology) are used to obtain IOP measurements in veterinary medicine. Objective: To compare and evaluate the accuracy of four handheld tonometers in measuring IOP using different methodologies in healthy horses. Methods: In vivo experiment and cross-sectional survey of healthy horses. Methods: Intraocular pressure was measured in 72 eyes of 36 horses. ...
Komáromy AM, Rowlan JS, La Croix NC, Mangan BG.To describe the clinical phenotype and genetics of equine Multiple Congenital Ocular Anomalies (MCOA) syndrome in PMEL17 (Silver) mutant ponies. Methods: Five presumably unrelated ponies. Methods: The ponies were examined under field conditions in their barn by slit lamp biomicroscopy, indirect ophthalmoscopy, and applanation tonometry. Blood was collected and genomic DNA extracted for MCOA genotyping using the PMEL17ex11 marker. Results: One pony solely presented with temporal ciliary body cysts, suggestive of the less severe Cyst phenotype of MCOA; the animal was heterozygous at the MCOA loc...
Michau TM, Schwabenton B, Davidson MG, Gilger BC.To characterize superficial, nonhealing corneal ulcers in the horse and to assess the affect of age, breed, sex, inciting cause of the ulcer, and treatment on healing time of these ulcers. Methods: Retrospective study. Methods: Twenty-three horses with superficial, nonhealing corneal ulcerations. Methods: Medical records from 1989 to 2003 of horses diagnosed with superficial, nonhealing corneal ulcers were reviewed. Signalment, duration of clinical signs, ophthalmic abnormalities, treatment and response to treatment were recorded. Horses were treated, in addition to medical therapy, using debr...
Knickelbein KE, Lassaline ME, Bellone RR.To document a case of limbal squamous cell carcinoma (SCC) in a Rocky Mountain Horse stallion determined to be homozygous for the genetic risk factor (DDB2 c.1013C>T) strongly associated with the disease in Haflinger and Belgian horses, and to determine the frequency of this allele in a larger population of Rocky Mountain Horses. Methods: One privately owned Rocky Mountain Horse and 84 Rocky Mountain Horses screened for allelic frequency. Methods: A complete ophthalmic examination was performed on a Rocky Mountain Horse stallion for assessment of a mass affecting the right eye. A clinical diag...
Jarry J, De Raeve Y, Dugdale A, Simon V, Vandeweerd JM.Severe ophthalmic conditions such as trauma, uveitis, corneal damage, or neoplasia can lead to eye removal surgery. Poor cosmetic appearance resulting from the sunken orbit ensues. The aim of this study was to demonstrate the feasibility of manufacturing a custom-made 3D-printed orbital implant made of biocompatible material for the enucleated horse and usable in conjunction to a corneoscleral shell. Blender, a 3D-image software, was used for prototype design. Twelve cadaver heads of adult Warmbloods were collected from the slaughterhouse. On each head, one eye was removed via a modified trans...
Bendlin A, Gemensky-Metzler AJ, Diaz-Campos D, Newbold GM, Miller EJ, Chandler HL.To compare results from a commercial next-generation sequencing (NGS) service to corneal cytology and culture for identification of causative organisms in veterinary patients presenting for infectious ulcerative keratitis (IUK). Methods: Swabs for corneal aerobic and fungal cultures and DNA swabs for NGS were submitted for canine and equine normal controls (n = 11 and n = 4, respectively) and IUK patients (n = 22 and n = 8, respectively) for which microbrush cytology specimens confirmed the presence of infectious organisms. The sensitivity of the NGS results was compared with bacterial...
Marsh RJ, Fraunfelder FT, McGill JI.The clinical differentiation of corneal epithelial lesions due to herpes simplex or herpes zoster may be confusing. Practical clinical tests, including the use of topical ocular stains, are useful to differentiate corneal epithelial lesions caused by these two viruses. Two distinctive types of zoster corneal epithelial disease may be seen; an early dendritic form, and a delayed form characterized by corneal mucus plaques that may take a dendriform pattern. These plaques are composed of mucus that is adherent to swollen, degenerating epithelial cells. The clinical differentiation between these ...
Rohrbach BW, Ward DA, Hendrix DV, Cawrse-Foss M, Moyers TD.To evaluate the effect of vaccination against leptospirosis on frequency and days to recurrence of uveitis and progression of disease in horses with equine recurrent uveitis (ERU). Methods: Forty-one horses with ERU. Methods: Horses were randomly assigned to experimental (vaccinated) or control groups. Vaccine containing six serovars of Leptospira or placebo was administered, an ophthalmic examination performed and blood samples drawn on days 0, 28, 180 and 365. Antibody titers were measured against each serovar. Recurrence of uveitis was verified by ophthalmic examination. Results of the init...
Pirie CG, Pizzirani S. To describe a novel digital single lens reflex (dSLR) camera adaptor for anterior and posterior segment photography. Methods: The adaptor was used to evaluate canine, feline, and equine patients presenting to Tufts Ophthalmology service. Anterior segment imaging was conducted with the adaptor mounted between a dSLR camera body (Canon 7D) and a macro lens (Canon EF-S 60mm/f2.8). Posterior segment imaging was performed with the aid of an indirect ophthalmic lens mounted in front of the macro lens. Coaxial illumination during viewing was provided by a single white light-emitting diode (LE...
Labelle AL, Hamor RE, Townsend WM, Mitchell MA, Zarfoss MK, Breaux CB, Thomasy SM, Hall T.To determine types and frequency of ophthalmic lesions detected in neonatal foals evaluated for nonophthalmic disease at 3 veterinary referral hospitals and to investigate associations between systemic and ophthalmic diseases in these foals. Methods: Prospective cross-sectional study. Methods: 70 foals < 30 days old. Methods: Complete ophthalmic examinations were performed. Signalment, clinical signs, mentation during ophthalmic examination, results of clinicopathologic tests, and diagnosis of systemic disease were recorded. Descriptive data analysis including a χ(2) test for associations was...
Cavens VJ, Gemensky-Metzler AJ, Wilkie DA, Weisbrode SE, Lehman AM.To describe the long-term histologic and intraocular pressure (IOP) lowering effects of diode laser transscleral cyclophotocoagulation (TSCP) on the normal equine eye. Methods: Eight normal adult horses. Methods: TSCP was performed in one randomly assigned eye. Sixty spots were treated at settings of 1500 ms and 1500 mW. Two horses were randomly selected for euthanasia at 2, 4, 12, or 24 weeks post-TSCP. Both eyes were enucleated and histologically evaluated. Intraocular pressure was measured by applanation tonometry prior to TSCP, immediately post-TSCP, twice daily for 7 days post-TSCP and th...
Hoerdemann M, Yarbrough T.To describe the technique, postoperative complications, and outcome after autologous fascia lata grafting with conjunctival flap overlay in horses with ulcerative keratitis and keratomalacia. Methods: Retrospective case series. Methods: Eleven horses with ulcerative keratitis and keratomalacia. Methods: Horses included had undergone fascia lata grafting with conjunctival flap overlay due to impending or recent corneal perforation. Preceding therapy, lesion characteristics, postoperative complications, and short- and long-term outcomes were recorded. Results: Postoperative complications include...
Townsend WM, Wasserman N, Jacobi S.Intraocular lenses (IOLs) have been implanted in adult equine eyes after cataract surgery. Foals and weanlings comprise a large proportion of those horses undergoing cataract surgery. Due to potential differences in the size and corneal curvature of the juvenile eye, it is not currently known whether implantation of adult IOLs is appropriate in foals and weanlings. The objective of the study was to measure the anterior chamber depth (ACD), central lens thickness (CLT), vitreous chamber depth (VCD), axial globe length (AGL) and corneal curvature of horses less than one year of age. The axial di...
Smith P, Samuelson D, Brooks D.The anterior vasculature of the pony eye was examined by the corrosion cast method. The anterior segment of the pony eye has a vascular pattern which is similar but distinct from that of other mammalian species. Large iridal veins collateralized directly with the anterior vortex venous system. The intrascleral plexus was present but formed a fine, radially oriented, extensive network. This contrasted to the circumferential larger-diameter intrascleral plexus noted in dogs and the canal of Schlemm present in primates. The intrascleral plexus only drained posteriorly in the pony as compared to t...
Brem S, Gerhards H, Wollanke B, Meyer P, Kopp H.Vitreous samples from 43 horses which underwent vitrectomy because of equine recurrent uveitis (ERU) were cultured for leptospires. Out of 4 vitreous samples (4/43 = 9%), leptospires could be isolated. In 3 cases, serovar grippotyphosa, and in one case, a serovar out of the serogroup Australis were identified. So for the first time, in several horses with ERU in vivo cultures of vitreous material were positive for leptospires. A strong evidence of association between leptospiral infection and uveitis is discussed for many years. In this investigation the leptospiral etiology is confirmed. Vitr...
Wada S, Yoshinari M, Katayama Y, Anzai T, Wada R, Akuzawa M.A 2-year-old Thoroughbred filly presented with ocular pain and epiphora of the left eye. The pupil was miotic and the cornea edematous near the ventro-temporal limbus, but did not retain any fluorescein. The topical antibiotics and atropine and diclofenac, and systemic flunixin meglumine and antibiotic therapy did not resolve the condition. A pink and fleshy infiltrate developed near the limbus indicating nonulcerative keratouveitis. The anterior uveitis deteriorated as manifested by the presence of dyscoria, hypopyon, and organized fibrin in the anterior chamber. Ocular signs were improved by...
Brooks DE, Clark CK, Lester GD.Corneal touch threshold (CTT) was measured in sick neonatal foals, healthy foals, and healthy adult horses with a Cochet-Bonnet aesthesiometer. The mean overall CTT for the adult horses, sick foals, and healthy foals was 4.82 +/- 0.87 cm, 3.21 +/- 0.24 cm, and 5.01 +/- 0.61 cm, respectively. The central cornea of adult horses was more sensitive than the limbal cornea. Corneal sensitivity was significantly reduced in sick neonatal foals compared to adults. The mean Schirmer I tear test values were significantly lower in foals than adults, and were 14.2 +/- 1.0 mm, 12.8 +/- 2.4 mm, and 18.3 +/- ...
Knickelbein KE, Lassaline ME, Kim S, Scharbrough MS, Thomasy SM.To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness measurements between UBM and ultrasonic pachymetry. Methods: Sixty eyes of 30 healthy adult horses aged 8-24 years. Methods: Ultrasonic pachymetry (velocity of 1640 m/s) was utilized to obtain measurements of the central, superior, temporal, inferior, and nasal cornea. Triplicate images of the same corneal locations were acquired using UBM (50 MHz). Images of the axial anterior chamber were used to measure ACD. Intraocular pres...
Peyrecave-Capo X, Saulnier N, Maddens S, Gremillet B, Desjardins I.Human autologous serum (AS) and umbilical cord serum (UCS) both contain growth and neurotrophic factors that promote corneal healing. Unassigned: Our objectives were to compare equine AS and UCS cytokine and growth factor profiles and to assess the safety and clinical feasibility of the therapeutic use of UCS eye drops in cases of spontaneous complex ulcers. Unassigned: Prospective clinical trial. Unassigned: Vitamin A insulin growth factor, platelet-derived growth factor-BB, transforming growth factor (TGF)-β1 (enzyme-linked immunosorbent assay), interleukin (IL)-1β, IL-6, interferon-γ, an...
Herb VM, Zehetner V, Blohm KO.This is the first description of Multiple Congenital Ocular Anomalies (MCOA) in a silver coat Missouri Fox Trotter determined to be heterozygous for the Silver PMEL17 missense mutation associated with MCOA and a silver coat in other breeds. The stallion was treated for meningoencephalitis and bilateral uveitis of unknown origin. A complete ophthalmic examination and ocular ultrasonography were performed. As an incidental finding, the patient exhibited bilateral cystic lesions restricted to the temporal anterior uvea consistent with the Cyst phenotype and was genotyped heterozygous for the Silv...
Monk CS, Brooks DE, Granone T, Garcia-Pereira FL, Melesko A, Plummer CE.To measure intraocular pressure (IOP) in horses during hoisting after induction of anesthesia. Methods: Prospective nonrandomized clinical study. Methods: Eighteen healthy adult horses aged [mean±standard deviation (SD)] 10±4.2 years and weighing 491±110 kg anesthetized for elective procedures. Methods: IOP was measured in the superior eye of each horse based on planned recumbency after induction of anesthesia. Measurements were taken directly after premedication with xylazine or detomidine with butorphanol, after induction with diazepam-ketamine, after intubation, when suspended by the ho...
Margalit E, Sadda SR.A variety of disease processes can affect the retina and/or the optic nerve, including vascular or ischemic disease, inflammatory or infectious disease, and degenerative disease. These disease processes may selectively damage certain parts of the retina or optic nerve, and the specific areas that are damaged may have implications for the design of potential therapeutic visual prosthetic devices. Outer retinal diseases include age-related macular degeneration, pathologic myopia, and retinitis pigmentosa. Although the retinal photoreceptors may be lost, the inner retina is relatively well-preser...
Badial PR, Cisneros-Àlvarez LE, Brandão CV, Ranzani JJ, Tomaz MA, Machado VM, Borges AS.The aim of this study was to compare ocular dimensions, corneal curvature, and corneal thickness between horses affected with hereditary equine regional dermal asthenia (HERDA) and unaffected horses. Methods: Five HERDA-affected quarter horses and five healthy control quarter horses were used. Methods: Schirmer's tear test, tonometry, and corneal diameter measurements were performed in both eyes of all horses prior to ophthalmologic examinations. Ultrasonic pachymetry was performed to measure the central, temporal, nasal, dorsal, and ventral corneal thicknesses in all horses. B-mode ultrasound...
Blair MJ, Gionfriddo JR, Polazzi LM, Sojka JE, Pfaff AM, Bingaman DP.To evaluate the feasibility of using a subconjunctivally implanted micro-osmotic pump for continuous delivery of medication to the eyes of horses- during a 7-day period. Methods: 4 healthy adult horses. Methods: With horses restrained in a standing position, micro-osmotic pumps were implanted subconjunctivally in each eye for 7 days. The treatment eye received an atropine-loaded micro-osmotic pump (100 microl of 1.5% atropine), and the contralateral eye received a sterile saline-loaded pump (100 microl of 0.9% NaCl) as a control treatment. Pupil size was measured at 12-hour intervals until val...
Zeiss C, Neaderland M, Yang FC, Terwilliger G, Compton S.To assess the diagnostic utility of fungal polymerase chain reaction (PCR) in forty-three horses with naturally acquired corneal ulcers presenting to a private practice. Methods: Routine evaluation of cytologic, histologic, and microbiologic samples was performed. Two PCR approaches were compared - generic and specific fungal nested PCR followed by sequencing and quantitative PCR (qPCR). PCRs were applied to pure control fungal cultures, corneal tissue from ulcerated eyes and in a subset of 9 horses, to swabs from contralateral normal eyes. Results: The expected fungus was identified by nested...
Tahoun A, Elnafarawy HK, El-Sharkawy H, Rizk AM, Alorabi M, El-Shehawi AM, Youssef MA, Ibrahim HMM, El-Khodery S.This work aimed to characterize S. aureus isolates from the eyes of healthy and clinically affected equines in the Kafrelsheikh Governorate, Egypt. A total of 110 animals were examined for the presence of S. aureus, which was isolated from 33 animals with ophthalmic lesions and 77 healthy animals. We also investigated the antimicrobial resistance profile, oxacillin resistance mechanism, and the major virulence factors implicated in many studies of the ocular pathology of pathogenic S. aureus. The association between S. aureus eye infections and potential risk factors was also investigated. The...
